I took a cruise for my honeymoon several years ago. I had no issues on the ship except for seasickness (I highly recommend Bonine for this as the patches and other stuff my Cd friend takes made him more sick). I did eat carefully... but there were so many choices on ship that I could always find something I could eat. The buffets have lots of bread and other things that were my safe foods.
In port, I just ordered bottled drinks and NO ICE. Ice is not always made from purified water in the small countries we visited. Mostly, I only ate on board the ship
I hope you can relax and enjoy the cruise!